Medical tubes and methods of manufacture

ABSTRACT

The disclosure relates to medical tubes and methods of manufacturing medical tubes. The tube may be a composite structure made of two or more distinct components that are spirally wound to form an elongate tube. For example, one of the components may be a spirally wound elongate hollow body, and the other component may be an elongate structural component also spirally wound between turns of the spirally wound hollow body The tube need not be made from distinct components, however. For instance, an elongate hollow body formed (e.g., extruded) from a single material may be spirally wound to form an elongate tube. The elongate hollow body itself may in transverse cross-section have a thin wall portion and a relatively thicker or more rigid reinforcement portion. The tubes can be incorporated into a variety of medical circuits or may be employed for other medical uses.

BACKGROUND Field

This disclosure relates generally to tubes suitable for medical use, andin particular to tubes for use in medical circuits suitable forproviding gases to and/or removing gases from a patient, such as inpositive airway pressure (PAP), respirator, anaesthesia, ventilator, andinsufflation systems.

Description of the Related Art

In medical circuits, various components transport warm and/or humidifiedgases to and from patients. For example, in some breathing circuits suchas PAP or assisted breathing circuits, gases inhaled by a patient aredelivered from a heater-humidifier through an inspiratory tube. Asanother example, tubes can deliver humidified gas (commonly CO₂) intothe abdominal cavity in insufflation circuits. This can help prevent“drying out” of the patient's internal organs, and can decrease theamount of time needed for recovery from surgery. Unheated tubing allowssignificant heat loss to ambient cooling. This cooling may result inunwanted condensation or “rainout” along the length of the tubingtransporting warm, humidified air. A need remains for tubing thatinsulates against heat loss and, for example, allows for improvedtemperature and/or humidity control in medical circuits.

SUMMARY

Medical tubes and methods of manufacturing medical tubes are disclosedherein in various embodiments. In some embodiments, the tube may be acomposite structure made of two or more distinct components that arespirally wound to form an elongate tube. For example, one of thecomponents may be a spirally wound elongate hollow body, and the othercomponent may be an elongate structural component also spirally woundbetween turns of the spirally wound hollow body In other embodiments,the tube need not be made from distinct components. For instance, anelongate hollow body formed (e.g., extruded) from a single material maybe spirally wound to form an elongate tube. The elongate hollow bodyitself may in transverse cross-section have a thin wall portion and arelatively thicker or more rigid reinforcement portion. The tubes can beincorporated into a variety of medical circuits or may be employed forother medical uses.

In at least one embodiment, a composite tube can comprise a firstelongate member comprising a hollow body spirally wound to form at leastin part an elongate tube having a longitudinal axis, a lumen extendingalong the longitudinal axis, and a hollow wall surrounding the lumen. Asecond elongate member may be spirally wound and joined between adjacentturns of the first elongate member, the second elongate member formingat least a portion of the lumen of the elongate tube. The name “firstelongate member” and “second elongate member” do not necessarily connotean order, such as the order in which the components are assembled. Asdescribed herein, the first elongate member and the second elongatemember can also be portions of a single tube-shaped element.

In various embodiments, the foregoing component has one, some, or all ofthe following properties, as well as properties described elsewhere inthis disclosure.

The first elongate member can be a tube. The first elongate member canform in longitudinal cross-section a plurality of bubbles with aflattened surface at the lumen. Adjacent bubbles can be separated by agap above the second elongate member, or may not be directly connectedto each other. The bubbles can have perforations. The second elongatemember can have a longitudinal cross-section that is wider proximal thelumen and narrower at a radial distance from the lumen. Specifically,the second elongate member can have a longitudinal cross-section that isgenerally triangular, generally T-shaped, or generally Y-shaped. One ormore conductive filaments can be embedded or encapsulated in the secondelongate member. The one or more conductive filaments can be heatingfilaments (or more specifically, resistance heating filaments) and/orsensing filaments. The tube can comprise pairs of conductive filaments,such as two or four conductive filaments. Pairs of conductive filamentscan be formed into a connecting loop at one end of the composite tube.The one or more conductive filaments can be spaced from the lumen wall.In at least one embodiment, the second elongate member can have alongitudinal cross-section that is generally triangular, generallyT-shaped, or generally Y-shaped, and one or more conductive filamentscan be embedded or encapsulated in the second elongate member onopposite sides of the triangle, T-shape, or Y-shape.

The foregoing component according to any or all of the precedingembodiments can be incorporated into a medical circuit component, aninspiratory tube, an expiratory tube, a PAP component, an insufflationcircuit, an exploratory component, or a surgical component, among otherapplications.

A method of manufacturing a composite tube is also disclosed. Theresulting tube can have one, some, or all of the properties describedabove or anywhere in this disclosure. In at least one embodiment, themethod comprises providing a first elongate member comprising a hollowbody and a second elongate member configured to provide structuralsupport for the first elongate member. The second elongate member isspirally wrapped around a mandrel with opposite side edge portions ofthe second elongate member being spaced apart on adjacent wraps, therebyforming a second-elongate-member spiral. The first elongate member isspirally wrapped around the second-elongate-member spiral, such thatportions of the first elongate member overlap adjacent wraps of thesecond-elongate-member spiral and a portion of the first elongate memberis disposed adjacent the mandrel in the space between the wraps of thesecond-elongate-member spiral, thereby forming a first-elongate-memberspiral.

In various embodiments, the foregoing method can comprise one, some, orall of the following. The method can comprise supplying air at apressure greater than atmospheric pressure to an end of the firstelongate member. The method can comprise cooling thesecond-elongate-member spiral and the first-elongate-member spiral,thereby forming a composite tube having a lumen extending along alongitudinal axis and a hollow space surrounding the lumen. The methodcan comprise forming the first elongate member. The method can compriseextruding the first elongate member with a first extruder. The methodcan comprise forming the second elongate member. The method can compriseextruding the second elongate member with a second extruder. The secondextruder can be configured to encapsulate one or more conductivefilaments in the second elongate member. Forming the second elongatemember can comprise embedding conductive filaments in the secondelongate member. The conductive filaments can be non-reactive with thesecond elongate member. The conductive filaments can comprise alloys ofaluminum or copper or other conductive materials. The method cancomprise forming pairs of conductive filaments into a connecting loop atone end of the composite tube. The first extruder can be distinct fromthe second extruder.

A medical tube is also disclosed. In at least one embodiment, the tubecomprises an elongate hollow body spirally wound to form an elongatetube having a longitudinal axis, a lumen extending along thelongitudinal axis, and a hollow wall surrounding the lumen, wherein theelongate hollow body has in transverse cross-section a wall defining atleast a portion of the hollow body. The tube can further comprise areinforcement portion extending along a length of the elongate hollowbody being spirally positioned between adjacent turns of the elongatehollow body, wherein the reinforcement portion forms a portion of thelumen of the elongate tube. The reinforcement portion can be relativelythicker or more rigid than the wall of the elongate hollow body.

In various embodiments, the foregoing tube has one, some, or all of thefollowing properties, as well as properties described elsewhere in thisdisclosure. The reinforcement portion can be formed from the same pieceof material as the elongate hollow body. The elongate hollow body intransverse cross-section can comprise two reinforcement portions onopposite sides of the elongate hollow body, wherein spiral winding ofthe elongate hollow body joins adjacent reinforcement portions to eachother such that opposite edges of the reinforcement portions touch onadjacent turns of the elongate hollow body. Opposite side edges of thereinforcement portions can overlap on adjacent turns of the elongatehollow body. The reinforcement portion can be made of a separate pieceof material than the elongate hollow body. The hollow body can form inlongitudinal cross-section a plurality of bubbles with a flattenedsurface at the lumen. The bubbles can have perforations. The medicaltube can also comprise one or more conductive filaments embedded orencapsulated within the reinforcement portion. The conductive filamentcan be a heating filament and/or or sensing filament. The medical tubecan comprise two conductive filaments, wherein one conductive filamentis embedded or encapsulated in each of the reinforcement portions. Themedical tube can comprise two conductive filaments positioned on onlyone side of the elongate hollow body. Pairs of conductive filaments canbe formed into a connecting loop at one end of the elongate tube. Theone or more filaments can be spaced from the lumen wall.

The foregoing tube according to any or all of the preceding embodimentscan be incorporated into a medical circuit component, an inspiratorytube, an expiratory tube, a PAP component, an insufflation circuit, anexploratory component, or a surgical component, among otherapplications.

A method of manufacturing a medical tube is also disclosed. In at leastone embodiment, the method comprises spirally winding an elongate hollowbody around a mandrel to form an elongate tube having a longitudinalaxis, a lumen extending along the longitudinal axis, and a hollow wallsurrounding the lumen, wherein the elongate hollow body has intransverse cross-section a wall defining at least a portion of thehollow body and two reinforcement portions on opposite sides of theelongate body forming a portion of the wall of the lumen, the tworeinforcement portions being relatively thicker or more rigid than thewall defining at least a portion of the hollow body. The method canfurther comprise joining adjacent reinforcement portions to each othersuch that opposite edges of the reinforcement portions touch on adjacentturns of the elongate hollow body.

In various embodiments, the foregoing method can comprise one, some, orall of the following or any other properties described elsewhere in thisdisclosure. Joining adjacent reinforcement portions to each other cancause edges of the reinforcement portions to overlap. The method canfurther comprise supplying air at a pressure greater than atmosphericpressure to an end of the elongate hollow body. The method can furthercomprise cooling the elongate hollow body to join the adjacentreinforcement portions to each other. The method can further compriseextruding the elongate hollow body. The method can further compriseembedding conductive filaments in the reinforcement portions. The methodcan further comprise forming pairs of conductive filaments into aconnecting loop at one end of the elongate tube.

For purposes of summarizing the invention, certain aspects, advantagesand novel features of the invention have been described herein. It is tobe understood that not necessarily all such advantages may be achievedin accordance with any particular embodiment of the invention. Thus, theinvention may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments that implement the various features of the disclosedsystems and methods will now be described with reference to thedrawings. The drawings and the associated descriptions are provided toillustrate embodiments and not to limit the scope of the disclosure.

FIG. 1 shows a schematic illustration of a medical circuit incorporatingone or more medical tubes.

FIG. 2A shows a side-plan view of a section of an example compositetube.

FIG. 2B shows a longitudinal cross-section of a top portion a tubesimilar to the example composite tube of FIG. 2A.

FIG. 2C shows another longitudinal cross-section illustrating a firstelongate member in the composite tube.

FIG. 2D shows another longitudinal cross-section of a top portion of atube.

FIG. 2E shows another longitudinal cross-section of a top portion of atube.

FIG. 3A shows a transverse cross-section of a second elongate member inthe composite tube.

FIG. 3B shows another transverse cross-section of a second elongatemember.

FIG. 3C shows another example second elongate member.

FIG. 3D shows another example second elongate member.

FIG. 3E shows another example second elongate member.

FIG. 3F shows another example second elongate member.

FIG. 3G shows another example second elongate member.

FIG. 4A shows an aspect in a method for forming the composite tube.

FIG. 4B shows a spiral-wound second elongate member.

FIG. 4C shows another aspect in a method for forming the composite tube.

FIG. 4D shows another aspect in a method for forming the composite tube.

FIG. 4E shows another aspect in a method for forming the composite tube.

FIG. 4F shows another aspect in a method for forming the composite tube.

FIGS. 5A-5B shows another example illustrating a single elongate hollowbody being spirally wound to form a medical tube.

FIGS. 5C-5F shows examples of other single elongate hollow bodies beingspirally wound to form a medical tube.

FIG. 6 shows an example medical circuit according to at least oneembodiment.

FIG. 7 shows an insufflation system according to at least oneembodiment.

FIG. 8 is a schematic illustration of a coaxial tube, according to atleast one embodiment.

FIGS. 9A-C show examples of first elongate member shapes configured toimprove thermal efficiency.

FIGS. 9D-F show examples of filament arrangements configured to improvethermal efficiency.

FIGS. 10A-C show examples of first elongate member stacking.

FIGS. 11A-D demonstrate radius of curvature properties of tubesaccording to various embodiments.

Throughout the drawings, reference numbers are re-used to indicatecorrespondence between referenced (or similar) elements. In addition,the first digit of each reference number indicates the figure in whichthe element first appears.

DETAILED DESCRIPTION

Details regarding several illustrative embodiments for implementing theapparatuses and methods described herein are described below withreference to the figures. The invention is not limited to thesedescribed embodiments.

Breathing Circuit Comprising One or More Medical Tubes

For a more detailed understanding of the disclosure, reference is firstmade to FIG. 1, which shows a breathing circuit according to at leastone embodiment, which includes one or more medical tubes. Tube is abroad term and is to be given its ordinary and customary meaning to aperson of ordinary skill in the art (that is, it is not to be limited toa special or customized meaning) and includes, without limitation,non-cylindrical passageways. Certain embodiments may incorporate acomposite tube, which may generally be defined as a tube comprising twoor more portions, or, specifically, in some embodiments, two or morecomponents, as described in greater detail below. Such a breathingcircuit can be a continuous, variable, or bi-level positive airwaypressure (PAP) system or other form of respiratory therapy.

Gases can be transported in the circuit of FIG. 1 as follows. Dry gasespass from a ventilator/blower 105 to a humidifier 107, which humidifiesthe dry gases. The humidifier 107 connects to the inlet 109 (the end forreceiving humidified gases) of the inspiratory tube 103 via a port 111,thereby supplying humidified gases to the inspiratory tube 103. Aninspiratory tube is a tube that is configured to deliver breathing gasesto a patient, and may be made from a composite tube as described infurther detail below. The gases flow through the inspiratory tube 103 tothe outlet 113 (the end for expelling humidified gases), and then to thepatient 101 through a patient interface 115 connected to the outlet 113.

An expiratory tube 117 also connects to the patient interface 115. Anexpiratory tube is a tube that is configured to move exhaled humidifiedgases away from a patient. Here, the expiratory tube 117 returns exhaledhumidified gases from the patient interface 115 to the ventilator/blower105.

In this example, dry gases enter the ventilator/blower 105 through avent 119. A fan 121 can improve gas flow into the ventilator/blower bydrawing air or other gases through vent 119. The fan 121 can be, forinstance, a variable speed fan, where an electronic controller 123controls the fan speed. In particular, the function of the electroniccontroller 123 can be controlled by an electronic master controller 125in response to inputs from the master controller 125 and a user-setpredetermined required value (preset value) of pressure or fan speed viaa dial 127.

The humidifier 107 comprises a humidification chamber 129 containing avolume of water 130 or other suitable humidifying liquid. Preferably,the humidification chamber 129 is removable from the humidifier 107after use. Removability allows the humidification chamber 129 to be morereadily sterilized or disposed. However, the humidification chamber 129portion of the humidifier 107 can be a unitary construction. The body ofthe humidification chamber 129 can be formed from a non-conductive glassor plastics material. But the humidification chamber 129 can alsoinclude conductive components. For instance, the humidification chamber129 can include a highly heat-conductive base (for example, an aluminumbase) contacting or associated with a heater plate 131 on the humidifier107.

The humidifier 107 can also include electronic controls. In thisexample, the humidifier 107 includes an electronic, analog or digitalmaster controller 125. Preferably, the master controller 125 is amicroprocessor-based controller executing computer software commandsstored in associated memory. In response to the user-set humidity ortemperature value input via a user interface 133, for example, and otherinputs, the master controller 125 determines when (or to what level) toenergize heater plate 131 to heat the water 130 within humidificationchamber 129.

Any suitable patient interface 115 can be incorporated. Patientinterface is a broad term and is to be given its ordinary and customarymeaning to a person of ordinary skill in the art (that is, it is not tobe limited to a special or customized meaning) and includes, withoutlimitation, masks (such as tracheal mask, face masks and nasal masks),cannulas, and nasal pillows. A temperature probe 135 can connect to theinspiratory tube 103 near the patient interface 115, or to the patientinterface 115. The temperature probe 135 monitors the temperature nearor at the patient interface 115. A heating filament (not shown)associated with the temperature probe can be used to adjust thetemperature of the patient interface 115 and/or inspiratory tube 103 toraise the temperature of the inspiratory tube 103 and/or patientinterface 115 above the saturation temperature, thereby reducing theopportunity for unwanted condensation.

In FIG. 1, exhaled humidified gases are returned from the patientinterface 115 to the ventilator/blower 105 via the expiratory tube 117.The expiratory tube 117 can also be a composite tube, as described ingreater detail below. However, the expiratory tube 117 can also be amedical tube as previously known in the art. In either case, theexpiratory tube 117 can have a temperature probe and/or heatingfilament, as described above with respect to the inspiratory tube 103,integrated with it to reduce the opportunity for condensation.Furthermore, the expiratory tube 117 need not return exhaled gases tothe ventilator/blower 105. Alternatively, exhaled humidified gases canbe passed directly to ambient surroundings or to other ancillaryequipment, such as an air scrubber/filter (not shown). In certainembodiments, the expiratory tube is omitted altogether.

Composite Tubes

FIG. 2A shows a side-plan view of a section of example composite tube201. In general, the composite tube 201 comprises a first elongatemember 203 and a second elongate member 205. Member is a broad term andis to be given its ordinary and customary meaning to a person ofordinary skill in the art (i.e., it is not to be limited to a special orcustomized meaning) and includes, without limitation, integral portions,integral components, and distinct components. Thus, although FIG. 2Aillustrates an embodiment made of two distinct components, it will beappreciated that in other embodiments (such as described in FIGS. 5A-5Dbelow), the first elongate member 203 and second elongate member 205 canalso represent regions in a tube formed from a single material. Thus,the first elongate member 203 can represent a hollow portion of a tube,while the second elongate member 205 represents a structural supportingor reinforcement portion of the tube which adds structural support tothe hollow portion. The hollow portion and the structural supportingportion can have a spiral configuration, as described herein. Thecomposite tube 201 may be used to form the inspiratory tube 103 and/orthe expiratory tube 117 as described above, a coaxial tube as describedbelow, or any other tubes as described elsewhere in this disclosure.

In this example, the first elongate member 203 comprises a hollow bodyspirally wound to form, at least in part, an elongate tube having alongitudinal axis LA-LA and a lumen 207 extending along the longitudinalaxis LA-LA. In at least one embodiment, the first elongate member 203 isa tube. Preferably, the first elongate member 203 is flexible.Furthermore, the first elongate member 203 is preferably transparent or,at least, semi-transparent or semi-opaque. A degree of opticaltransparency allows a caregiver or user to inspect the lumen 207 forblockage or contaminants or to confirm the presence of moisture. Avariety of plastics, including medical grade plastics, are suitable forthe body of the first elongate member 203. Examples of suitablematerials include Polyolefin elastomers, Polyether block amides,Thermoplastic co-polyester elastomers, EPDM-Polypropylene mixtures, andThermoplastic polyurethanes.

The hollow body structure of the first elongate member 203 contributesto the insulating properties to the composite tube 201. An insulatingtube 201 is desirable because, as explained above, it prevents heatloss. This can allow the tube 201 to deliver gas from aheater-humidifier to a patient while maintaining the gas's conditionedstate with minimal energy consumption.

In at least one embodiment, the hollow portion of the first elongatemember 203 is filled with a gas. The gas can be air, which is desirablebecause of its low thermal conductivity (2.62×10⁻² W/m·K at 300K) andvery low cost. A gas that is more viscous than air may alsoadvantageously be used, as higher viscosity reduces convective heattransfer. Thus, gases such as argon (17.72×10⁻³ W/m·K at 300K), krypton(9.43×10⁻³ W/m·K at 300K), and xenon (5.65×10⁻³ W/m·K at 300K) canincrease insulating performance. Each of these gases is non-toxic,chemically inert, fire-inhibiting, and commercially available. Thehollow portion of the first elongated member 203 can be sealed at bothends of the tube, causing the gas within to be substantially stagnant.Alternatively, the hollow portion can be a secondary pneumaticconnection, such as a pressure sample line for conveying pressurefeedback from the patient-end of the tube to a controller. The firstelongate member 203 can be optionally perforated. For instance, thesurface of the first elongate member 203 can be perforated on anoutward-facing surface, opposite the lumen 207. In another embodiment,the hollow portion of the first elongate member 203 is filled with aliquid. Examples of liquids can include water or other biocompatibleliquids with a high thermal capacity. For instance, nanofluids can beused. An example nanofluid with suitable thermal capacity compriseswater and nanoparticles of substances such as aluminum.

The second elongate member 205 is also spirally wound and joined to thefirst elongate member 203 between adjacent turns of the first elongatemember 203. The second elongate member 205 forms at least a portion ofthe lumen 207 of the elongate tube. The second elongate member 205 actsas structural support for the first elongate member 203.

In at least one embodiment, the second elongate member 205 is wider atthe base (proximal the lumen 207) and narrower at the top. For example,the second elongate member can be generally triangular in shape,generally T-shaped, or generally Y-shaped. However, any shape that meetsthe contours of the corresponding first elongate member 203 is suitable.

Preferably, the second elongate member 205 is flexible, to facilitatebending of the tube. Desirably; the second elongate member 205 is lessflexible than the first elongate member 203. This improves the abilityof the second elongate member 205 to structurally support the firstelongate member 203. For example, the modulus of the second elongatemember 205 is preferably 30-50 MPa (or about 30-50 MPa). The modulus ofthe first elongate member 203 is less than the modulus of the secondelongate member 205. The second elongate member 205 can be solid ormostly solid. In addition, the second elongate member 205 canencapsulate or house conductive material, such as filaments, andspecifically heating filaments or sensors (not shown). Heating filamentscan minimize the cold surfaces onto which condensate from moisture-ladenair can form. Heating filaments can also be used to alter thetemperature profile of gases in the lumen 207 of composite tube 201. Avariety of polymers and plastics, including medical grade plastics, aresuitable for the body of the second elongate member 205. Examples ofsuitable materials include Polyolefin elastomers, Polyether blockamides, Thermoplastic co-polyester elastomers, EPDM-Polypropylenemixtures and Thermoplastic polyurethanes. In certain embodiments, thefirst elongate member 203 and the second elongate member 205 may be madefrom the same material. The second elongate member 205 may also be madeof a different color material from the first elongate member 203, andmay be transparent, translucent or opaque. For example, in oneembodiment the first elongate member 203 may be made from a clearplastic, and the second elongate member 205 may be made from an opaqueblue (or other color) plastic.

This spirally-wound structure comprising a flexible, hollow body and anintegral support can provide crush resistance, while leaving the tubewall flexible enough to permit short-radius bends without kinking,occluding or collapsing. Preferably, the tube can be bent around a 25 mmdiameter metal cylinder without kinking, occluding, or collapsing, asdefined in the test for increase in flow resistance with bendingaccording to ISO 5367:2000(E). This structure also can provide a smoothlumen 207 surface (tube bore), which helps keep the tube free fromdeposits and improves gas flow. The hollow body has been found toimprove the insulating properties of a tube, while allowing the tube toremain light weight.

As explained above, the composite tube 201 can be used as an expiratorytube and/or an inspiratory tube in a breathing circuit, or a portion ofa breathing circuit. Preferably, the composite tube 201 is used at leastas an inspiratory tube.

FIG. 2B shows a longitudinal cross-section of a top portion of theexample composite tube 201 of FIG. 2A. FIG. 2B has the same orientationas FIG. 2A. This example further illustrates the hollow-body shape ofthe first elongate member 203. As seen in this example, the firstelongate member 203 forms in longitudinal cross-section a plurality ofhollow bubbles. Portions 209 of the first elongate member 203 overlapadjacent wraps of the second elongate member 205. A portion 211 of thefirst elongate member 203 forms the wall of the lumen (tube bore).

It was discovered that having a gap 213 between adjacent turns of thefirst elongate member 203, that is, between adjacent bubbles,unexpectedly improved the overall insulating properties of the compositetube 201. Thus, in certain embodiments, adjacent bubbles are separatedby a gap 213. Furthermore, certain embodiments include the realizationthat providing a gap 213 between adjacent bubbles increases the heattransfer resistivity (the R value) and, accordingly, decreases the heattransfer conductivity of the composite tube 201. This gap configurationwas also found to improve the flexibility of the composite tube 201 bypermitting shorter-radius bends. A T-shaped second elongate member 205,as shown in FIG. 2B, can help maintain a gap 213 between adjacentbubbles. Nevertheless, in certain embodiments, adjacent bubbles aretouching. For example, adjacent bubbles can be bonded together.

One or more conductive materials can be disposed in the second elongatemember 205 for heating or sensing the gas flow. In this example, twoheating filaments 215 are encapsulated in the second elongate member205, one on either side of the vertical portion of the “T.” The heatingfilaments 215 comprise conductive material, such as alloys of Aluminum(Al) and/or Copper (Cu), or conductive polymer. Preferably, the materialforming the second elongate member 205 is selected to be non-reactivewith the metal in the heating filaments 215 when the heating filaments215 reach their operating temperature. The filaments 215 may be spacedaway from lumen 207 so that the filaments are not exposed to the lumen207. At one end of the composite tube, pairs of filaments can be formedinto a connecting loop.

In at least one embodiment, a plurality of filaments are disposed in thesecond elongate member 205. The filaments can be electrically connectedtogether to share a common rail. For example, a first filament, such asa heating filament, can be disposed on a first side of the secondelongate member 205. A second filament, such as a sensing filament, canbe disposed on a second side of the second elongate member 205. A thirdfilament, such as a ground filament, can be disposed between the firstand second filaments. The first, second, and/or third filaments can beconnected together at one end of the second elongate member 205.

FIG. 2C shows a longitudinal cross-section of the bubbles in FIG. 2B. Asshown, the portions 209 of the first elongate member 203 overlappingadjacent wraps of the second elongate member 205 are characterized by adegree of bond region 217. A larger bond region improves the tubesresistance to delamination at the interface of the first and secondelongate members. Additionally or alternatively, the shape of the beadand/or the bubble can be adapted to increase the bond region 217. Forexample, FIG. 2D shows a relatively small bonding area on the left-handside. FIG. 9B also demonstrates a smaller bonding region. In contrast,FIG. 2E has a much larger bonding region than that shown in FIG. 2D,because of the size and shape of the bead. FIGS. 9A and 9C alsoillustrate a larger bonding region. Each of these figures is discussedin more detail below. It should be appreciated that although theconfigurations in FIGS. 2E, 9A, and 9C may be preferred in certainembodiments, other configurations, including those of FIGS. 2D, 9B, andother variations, may be utilized in other embodiments as may bedesired.

FIG. 2D shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 2D has the same orientation as FIG. 2B. Thisexample further illustrates the hollow-body shape of the first elongatemember 203 and demonstrates how the first elongate member 203 forms inlongitudinal cross-section a plurality of hollow bubbles. In thisexample, the bubbles are completely separated from each other by a gap213. A generally triangular second elongate member 205 supports thefirst elongate member 203.

FIG. 2E shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 2E has the same orientation as FIG. 2B. In theexample of FIG. 2E, the heating filaments 215 are spaced farther apartfrom each other than the filaments 215 in FIG. 2B. It was discoveredthat increasing the space between heating filaments can improve heatingefficiency, and certain embodiments include this realization. Heatingefficiency refers to the ratio of the amount of heat input to the tubeto the amount of energy output or recoverable from the tube. Generallyspeaking, the greater the energy (or heat) that is dissipated from thetube, the lower the heating efficiency. For improved heatingperformance, the heating filaments 215 can be equally (or about equally)spaced along the bore of the tube. Alternatively, the filaments 215 canbe positioned at extremities of the second elongate member 205, whichmay provide simpler manufacturing.

Reference is next made to FIGS. 3A through 3G which demonstrate exampleconfigurations for the second elongate member 205. FIG. 3A shows across-section of a second elongate member 205 having a shape similar tothe T-shape shown in FIG. 2B. In this example embodiment, the secondelongate member 205 does not have heating filaments. Other shapes forthe second elongate member 205 may also be utilized, includingvariations of the T-shape as described below and triangular shapes.

FIG. 3B shows another example second elongate member 205 having aT-shape cross-section. In this example, heating filaments 215 areembedded in cuts 301 in the second elongate member 205 on either side ofthe vertical portion of the “T.” In some embodiments, the cuts 301 canbe formed in the second elongate member 205 during extrusion. The cuts301 can alternatively be formed in the second elongate member 205 afterextrusion. For example, a cutting tool can form the cuts in the secondelongate member 205. Preferably, the cuts are formed by the heatingfilaments 215 as they are pressed or pulled (mechanically fixed) intothe second elongate member 205 shortly after extrusion, while the secondelongate member 205 is relatively soft. Alternatively, one or moreheating filaments can be mounted (e.g., adhered, bonded, or partiallyembedded) on the base of the elongate member, such that the filament(s)are exposed to the tube lumen. In such embodiments, it can be desirableto contain the filament(s) in insulation to reduce the risk of fire whena flammable gas such as oxygen is passed through the tube lumen.

FIG. 3C shows yet another example second elongate member 205 incross-section. The second elongate member 205 has a generally triangularshape. In this example, heating filaments 215 are embedded on oppositesides of the triangle.

FIG. 3D shows yet another example second elongate member 205 incross-section. The second elongate member 205 comprises four grooves303. The grooves 303 are indentations or furrows in the cross-sectionalprofile. In some embodiments, the grooves 303 can facilitate theformation of cuts (not shown) for embedding filaments (not shown). Insome embodiments, the grooves 303 facilitate the positioning offilaments (not shown), which are pressed or pulled into, and therebyembedded in, the second elongate member 205. In this example, the fourinitiation grooves 303 facilitate placement of up to four filaments,e.g., four heating filaments, four sensing filaments, two heatingfilaments and two sensing filaments, three heating filaments and onesensing filament, or one heating filament and three sensing filaments.In some embodiments, heating filaments can be located on the outside ofthe second elongate member 205. Sensing filaments can be located on theinside.

FIG. 3E shows still another example second elongate member 205 incross-section. The second elongate member 205 has a T-shape profile anda plurality of grooves 303 for placing heating filaments.

FIG. 3F shows yet another example second elongate member 205 incross-section. Four filaments 215 are encapsulated in the secondelongate member 205, two on either side of the vertical portion of the“T.” As explained in more detail below, the filaments are encapsulatedin the second elongate member 205 because the second elongate member 205was extruded around the filaments. No cuts were formed to embed theheating filaments 215. In this example, the second elongate member 205also comprises a plurality of grooves 303. Because the heating filaments215 are encapsulated in the second elongate member 205, the grooves 303are not used to facilitate formation of cuts for embedding heatingfilaments. In this example, the grooves 303 can facilitate separation ofthe embedded heating filaments, which makes stripping of individualcores easier when, for example, terminating the heating filaments.

FIG. 3G shows yet another example second elongate member 205 incross-section. The second elongate member 205 has a generally triangularshape. In this example, the shape of the second elongate member 205 issimilar to that of FIG. 3C, but four filaments 215 are encapsulated inthe second elongate member 205, all of which are central in the bottomthird of the second elongate member 205 and disposed along a generallyhorizontal axis.

As explained above, it can be desirable to increase the distance betweenfilaments to improve heating efficiency. In some embodiments, however,when heating filaments 215 are incorporated into the composite tube 201,the filaments 215 can be positioned relatively central in the secondelongate member 205. A centralized position promotes robustness of thecomposite tubing for reuse, due in part to the position reducing thelikelihood of the filament breaking upon repeating flexing of thecomposite tube 201. Centralizing the filaments 215 can also reduce therisk of an ignition hazard because the filaments 215 are coated inlayers of insulation and removed from the gas path.

As explained above, some of the examples illustrate suitable placementsof filaments 215 in the second elongate member 205. In the foregoingexamples comprising more than one filament 215, the filaments 215 aregenerally aligned along a horizontal axis. Alternative configurationsare also suitable. For example, two filaments can be aligned along avertical axis or along a diagonal axis. Four filaments can be alignedalong a vertical axis or a diagonal axis. Four filaments can be alignedin a cross-shaped configuration, with one filament disposed at the topof the second elongate member, one filament disposed at the bottom ofthe second elongate member (near the tube lumen), and two filamentsdisposed on opposite arms of a “T,” “Y,” or triangle base.

TABLES 1A and 1B show some preferred dimensions of medical tubesdescribed herein, as well as some preferred ranges for these dimensions.The dimensions refer to a transverse cross-section of a tube. In thesetables, lumen diameter represents the inner diameter of a tube. Pitchrepresents the distance between two repeating points measured axiallyalong the tube, namely, the distance between the tip of the verticalportions of adjacent “T”s of the second elongate member. Bubble widthrepresents the width (maximum outer diameter) of a bubble. Bubble heightrepresents the height of a bubble from the tube lumen. Bead heightrepresents the maximum height of the second elongate member from thetube lumen (e.g., the height of the vertical portion of the “T”). Beadwidth represents the maximum width of the second elongate member (e.g.,the width of the horizontal portion of the “T”). Bubble thicknessrepresents the thickness of the bubble wall.

TABLE 1A Infant Adult Dimension Dimension Feature (mm) Range (±) (mm)Range (±) Lumen diameter 11 1 18 5 Pitch 4.8 1 7.5 2 Bubble width 4.2 17 1 Bead width 2.15 1 2.4 1 Bubble height 2.8 1 3.5 0.5 Bead height 0.90.5 1.5 0.5 Bubble thickness 0.4 0.35 0.2 0.15

TABLE 1B Infant Adult Dimension Dimension Feature (mm) Range (±) (mm)Range (±) Lumen diameter 11 1 18 5 Pitch 4.8 1 7.5 2 Bubble width 4.2 17 1 Bead width 2.15 1 3.4 1 Bubble height 2.8 1 4.0 0.5 Bead height 0.90.5 1.7 0.5 Bubble thickness 0.4 0.35 0.2 0.15

TABLES 2A and 2B provide example ratios between the dimensions of tubefeatures for the tubes described in TABLES 1A and 1B respectively.

TABLE 2A Ratios Infant Adult Lumen diameter:Pitch 2.3:1 2.4:1Pitch:Bubble width 1.1:1 1.1:1 Pitch:Bead width 2.2:1 3.1:1 Bubblewidth:Bead width 2.0:1 2.9:1 Lumen diameter:Bubble height 3.9:1 5.1:1Lumen diameter:Bead height 12.2:1  12.0:1  Bubble height:Bead height3.1:1 2.3:1 Lumen diameter:Bubble thickness 27.5:1  90.0:1 

TABLE 2B Ratios Infant Adult Lumen diameter:Pitch 2.3:1 2.4:1Pitch:Bubble width 1.1:1 1.1:1 Pitch:Bead width 2.2:1 2.2:1 Bubblewidth:Bead width 2.0:1 2.1:1 Lumen diameter:Bubble height 3.9:1 4.5:1Lumen diameter:Bead height 12.2:1  10.6:1  Bubble height:Bead height3.1:1 2.4:1 Lumen diameter:Bubble thickness 27.5:1  90.0:1 

The following tables show some example properties of a composite tube(labeled “A”), described herein, having a heating filament integratedinside the second elongate member. For comparison, properties of aFisher & Paykel model RT100 disposable corrugated tube (labeled “B”)having a heating filament helically wound inside the bore of the tubeare also presented.

Measurement of resistance to flow (RTF) was carried out according toAnnex A of ISO 5367:2000(E). The results are summarized in TABLE 3. Asseen below, the RTF for the composite tube is lower than the RTF for themodel RT100 tube.

TABLE 3 RTF (cm H₂O) Flow rate (L/min) 3 20 40 60 A 0 0.05 0.18 0.38 B 00.28 0.93 1.99

Condensate or “rainout” within the tube refers to the weight ofcondensate collected per day at 20 L/min gas flow rate and roomtemperature of 18° C. Humidified air is flowed through the tubecontinuously from a chamber. The tube weights are recorded before andafter each day of testing. Three consecutive tests are carried out withthe tube being dried in between each test. The results are shown belowin TABLE 4. The results showed that rainout is significantly lower inthe composite tube than in the model RT100 tube.

TABLE 4 Tube A A A B B B (Day 1) (Day 2) (Day 3) (Day 1) (Day 2) (day 3)Weight 136.20 136.70 136.70 111.00 111.10 111.10 before (g) Weight139.90 140.00 139.20 190.20 178.80 167.10 after (g) Condensate 3.7 3.32.5 79.20 67.70 56.00 weight (g)

The power requirement refers to the power consumed during the condensatetest. In this test, the ambient air was held at 18° C. Humidificationchambers (see, e.g., the humidification chamber 129 in FIG. 1) werepowered by MR850 heater bases. The heating filaments in the tubes werepowered independently from a DC power supply. Different flow rates wereset and the chamber was left to settle to 37° C. at the chamber output.Then, the DC voltage to the circuits was altered to produce atemperature of 40° C. at the circuit output. The voltage required tomaintain the output temperature was recorded and the resulting powercalculated. The results are shown in TABLE 5. The results show thatcomposite Tube A uses significantly more power than Tube B. This isbecause Tube B uses a helical heating filament in the tube bore to heatthe gas from 37° C. to 40° C. The composite tube does not tend to heatgas quickly because the heating filament is in the wall of the tube(embedded in the second elongate member). Instead, the composite tube isdesigned to maintain the gas temperature and prevent rainout bymaintaining the tube bore at a temperature above the dew point of thehumidified gas.

TABLE 5 Flow rate (L/min) 40 30 20 Tube A, power required (W) 46.8 38.537.8 Tube B, power required (W) 28.0 27.5 26.8

Tube flexibility was tested by using a three-point bend test. Tubes wereplaced in a three point bend test jig and used along with an Instron5560 Test System instrument, to measure load and extension. Each tubesample was tested three times; measuring the extension of the tubeagainst the applied load, to obtain average respective stiffnessconstants. The average stiffness constants for Tube A and Tube B arereproduced in TABLE 6.

TABLE 6 Tube Stiffness (N/mm) A 0.028 B 0.088Methods of Manufacture

Reference is next made to FIGS. 4A through 4F which demonstrate examplemethods for manufacturing composite tubes.

Turning first to FIG. 4A, in at least one embodiment, a method ofmanufacturing a composite tube comprises providing the second elongatemember 205 and spirally wrapping the second elongate member 205 around amandrel 401 with opposite side edge portions 403 of the second elongatemember 205 being spaced apart on adjacent wraps, thereby forming asecond-elongate-member spiral 405. The second elongate member 205 may bedirectly wrapped around the mandrel in certain embodiments. In otherembodiments, a sacrificial layer may be provided over the mandrel.

In at least one embodiment, the method further comprises forming thesecond elongate member 205. Extrusion is a suitable method for formingthe second elongate member 205. The second extruder can be configured toextrude the second elongate member 205 with a specified bead height.Thus, in at least one embodiment, the method comprises extruding thesecond elongate member 205.

As shown in FIG. 4B, extrusion can be advantageous because it can allowheating filaments 215 to be encapsulated in the second elongate member205 as the second elongate member is formed 205, for example, using anextruder having a cross-head extrusion die. Thus, in certainembodiments, the method comprises providing one or more heatingfilaments 215 and encapsulated the heating filaments 215 to form thesecond elongate member 205. The method can also comprise providing asecond elongate member 205 having one or more heating filaments 215embedded or encapsulated in the second elongate member 205.

In at least one embodiment, the method comprises embedding one or morefilaments 215 in the second elongate member 205. For example, as shownin FIG. 4C, filaments 215 can be pressed (pulled or mechanicallypositioned) into the second elongate member 205 to a specified depth.Alternatively, cuts can be made in the second elongate member 205 to aspecified depth, and the filaments 215 can be placed into the cuts.Preferably, pressing or cutting is done shortly after the secondelongate member 205 is extruded and the second elongate member 205 issoft.

As shown in FIGS. 4D and 4E, in at least one embodiment, the methodcomprises providing the first elongate member 203 and spirally wrappingthe first elongate member 203 around the second-elongate-member spiral405, such that portions of the first elongate member 203 overlapadjacent wraps of the second-elongate-member spiral 405 and a portion ofthe first elongate member 203 is disposed adjacent the mandrel 401 inthe space between the wraps of the second-elongate-member spiral 405,thereby forming a first-elongate-member spiral 407. FIG. 4D shows suchan example method, in which heating filaments 215 are encapsulated inthe second elongate member 205, prior to forming thesecond-elongate-member spiral. FIG. 4E shows such an example method, inwhich heating filaments 215 are embedded in the second elongate member205, as the second-elongate-member spiral is formed. An alternativemethod of incorporating filaments 215 into the composite tube comprisesencapsulating one or more filaments 215 between the first elongatemember 203 and the second elongate member 205 at a region where thefirst elongate member 203 overlaps the second elongate member 205.

The above-described alternatives for incorporating one or more heatingfilaments 215 into a composite tube have advantages over the alternativeof having heating filaments in the gas path. Having the heatingfilament(s) 215 out of the gas path improves performance because thefilaments heat the tube wall where the condensation is most likely toform. This configuration reduces fire risk in high oxygen environmentsby moving the heating filament out of the gas path. This feature alsoreduces performance as it reduces the heating wires effectiveness atheating the gases that are passing through the tube. Nevertheless, incertain embodiments, a composite tube 201 comprises one or more heatingfilaments 215 placed within the gas path. For example, heating filamentscan be emplaced on the lumen wall (tube bore), for example, in a spiralconfiguration. An example method for disposing one or more heatingfilaments 215 on the lumen wall comprises bonding, embedding, orotherwise forming a heating filament on a surface of the second elongatemember 205 that, when assembled, forms the lumen wall. Thus, in certainembodiments, the method comprises disposing one or more heatingfilaments 215 on the lumen wall.

Regardless of whether the heating filaments 215 are embedded orencapsulated on the second elongate member 205 or disposed on the secondelongate member 205, or otherwise placed in or on the tube, in at leastone embodiment, pairs of filaments can be formed into a connecting loopat one end of the composite tube to form a circuit.

FIG. 4F shows a longitudinal cross-section of the assembly shown in FIG.4E, focusing on a top portion of the mandrel 401 and a top portion ofthe first-elongate-member spiral 407 and second-elongate-member spiral405. This example shows the second-elongate-member spiral 405 having aT-shaped second elongate member 205. As the second-elongate member isformed, heating filaments 215 are embedded in the second elongate member205. The right side of FIG. 4F shows the bubble-shaped profile of thefirst-elongate-member spiral, as described above.

The method can also comprise forming the first elongate member 203.Extrusion is a suitable method for forming the first elongate member203. Thus, in at least one embodiment, the method comprises extrudingthe first elongate member 203. The first elongate member 203 can also bemanufactured by extruding two or more portions and joining them to forma single piece. As another alternative, the first elongate member 203can also be manufactured by extruding sections that produce a hollowshape when formed or bonded adjacently on a spiral-tube forming process.

The method can also comprise supplying a gas at a pressure greater thanatmospheric pressure to an end of the first elongate member 203. The gascan be air, for example. Other gases can also be used, as explainedabove. Supplying a gas to an end of the first elongate member 203 canhelp maintain an open, hollow body shape as the first elongate member203 is wrapped around the mandrel 401. The gas can be supplied beforethe first elongate member 203 is wrapped around the mandrel 401, whilethe first elongate member 203 is wrapped around the mandrel 401, orafter the first elongate member 203 is wrapped around the mandrel 401.For instance, an extruder with an extrusion die head/tip combination cansupply or feed air into the hollow cavity of the first elongate member203 as the first elongate member 203 is extruded. Thus, in at least oneembodiment, the method comprises extruding the first elongate member 203and supplying a gas at a pressure greater than atmospheric pressure toan end of the first elongate member 203 after extrusion. A pressure of15 to 30 cm H₂O—(or about 15 to 30 cm H₂O) has been found to besuitable.

In at least one embodiment, the first elongate member 203 and the secondelongate member 205 are spirally wound about the mandrel 401. Forexample, the first elongate member 203 and second elongate member 205may come out of an extrusion die at an elevated temperature of 200° C.(or about 200° C.) or more and then be applied to the mandrel after ashort distance. Preferably, the mandrel is cooled using a water jacket,chiller, and/or other suitable cooling method to a temperature of 20° C.(or about 20° C.) or less, e.g., approaching 0° C. (or about 0° C.).After 5 (or about 5) spiral wraps, the first elongate member 203 andsecond elongate member 205 are further cooled by a cooling fluid (liquidor gas). In one embodiment, the cooling fluid is air emitted from a ringwith jets encircling the mandrel. After cooling and removing thecomponents from the mandrel, a composite tube is formed having a lumenextending along a longitudinal axis and a hollow space surrounding thelumen. In such an embodiment, no adhesive or other attachment mechanismis needed to connect the first and second elongate members. Otherembodiments may utilize an adhesive or other attachment mechanism tobond or otherwise connect the two members. In another embodiment, thesecond elongate member 205 after extrusion and placement of the heatingfilaments may be cooled to freeze the location of the heating filaments.The second elongate member 205 may then be re-heated when applied to themandrel to improve bonding. Example methods for re-heating include usingspot-heating devices, heated rollers, etc.

The method can also comprise formed pairs of heating or sensingfilaments into a connecting loop at one end of the composite tube. Forexample, end sections of two heating or sensing filaments can beextricated from the second elongate member 205 and then formed into aconnecting loop e.g., by tying, bonding, adhering, fusing, etc the twofilaments together. As another example, end sections of the heatingfilaments can be left free from the second elongate member 205 duringthe manufacturing process and then formed into a connecting loop whenthe composite tube is assembled.

Medical Tubes and Methods of Manufacture Using a Single Spirally WoundTube

Reference is next made to FIG. 5A through 5F which show transversecross-sections of tubes comprising a single tube-shaped element having afirst elongate member or portion 203 and a second elongate member orportion 205. As illustrated, the second elongate portions 205 areintegral with the first elongate portions 203, and extend along theentire length of the single tube-shaped element. In the embodimentsillustrated, the single tube-shaped element is an elongate hollow bodyhaving in transverse cross-section a relatively thin wall defining inpart the hollow portion 501, with two reinforcement portions 205 with arelatively greater thickness or relatively greater rigidity on oppositesides of the elongate hollow body adjacent the relatively thin wall.These reinforcement portions form a portion of the inner wall of thelumen 207 after the elongate hollow body is spirally wound, such thatthese reinforcement portions are also spirally positioned betweenadjacent turns of the elongate hollow body.

In at least one embodiment, the method comprises forming an elongatehollow body comprising the first elongate portion 203 and thereinforcement portion 205. Extrusion is a suitable method for formingthe elongate hollow body. Suitable cross-sectional shapes for thetube-shaped element are shown in FIG. 5A through 5F.

The elongate hollow body can be formed into a medical tube, as explainedabove, and the foregoing discussion is incorporated by this reference.For example, in at least one embodiment, a method of manufacturing amedical tube comprises spirally wrapping or winding the elongate hollowbody around a mandrel. This may be done at an elevated temperature, suchthat the elongate hollow body is cooled after being spirally wound tojoin adjacent turns together As shown in FIG. 5B, opposite side edgeportions of the reinforcement portions 205 can touch on adjacent turns.In other embodiments, opposite side edge portions of the second elongatemember 205 can overlap on adjacent turns, as shown in FIGS. 5D and 5E.Heating filaments 215 can be incorporated into the second elongatemember as explained above and as shown in FIG. 5A through 5F. Forexample, heating filaments may be provided on opposite sides of theelongate hollow body such as shown in FIGS. 5A-5D. Alternatively,heating filaments may be provided on only one side of the elongatehollow body, such as shown in FIGS. 5E-5F. Any of these embodimentscould also incorporate the presence of sensing filaments.

Medical Circuits

Reference is next made to FIG. 6, which shows an example medical circuitaccording to at least one embodiment. The circuit comprises one or morecomposite tubes as described above, namely for the inspiratory tube 103and/or the expiratory tube 117. The properties of the inspiratory tube103 and the expiratory tube 117 are similar to the tubes described abovewith respect to FIG. 1. The inspiratory tube 103 has an inlet 109,communicating with a humidifier 115, and an outlet 113, through whichhumidified gases are provided to the patient 101. The expiratory tube117 also has an inlet 109, which receives exhaled humidified gases fromthe patient, and an outlet 113. As described above with respect to FIG.1, the outlet 113 of the expiratory tube 117 can vent exhaled gases tothe atmosphere, to the ventilator/blower unit 115, to an airscrubber/filter (not shown), or to any other suitable location.

As described above, heating filaments 601 can be placed within theinspiratory tube 103 and/or the expiratory tube 117 to reduce the riskof rain out in the tubes by maintaining the tube wall temperature abovethe dew point temperature.

Component of an Insufflation System

Laparoscopic surgery, also called minimally invasive surgery (MIS), orkeyhole surgery, is a modern surgical technique in which operations inthe abdomen are performed through small incisions (usually 0.5 to 1.5cm) as compared to larger incisions needed in traditional surgicalprocedures. Laparoscopic surgery includes operations within theabdominal or pelvic cavities. During laparoscopic surgery withinsufflation, it may be desirable for the insufflation gas (commonlyCO₂) to be humidified before being passed into the abdominal cavity.This can help prevent “drying out” of the patient's internal organs, andcan decrease the amount of time needed for recovery from surgery.Insufflation systems generally comprise humidifier chambers that hold aquantity of water within them. The humidifier generally includes aheater plate that heats the water to create a water vapour that istransmitted into the incoming gases to humidify the gases. The gases aretransported out of the humidifier with the water vapor.

Reference is next made to FIG. 7, which shows an insufflation system701, according to at least one embodiment. The insufflation system 701includes an insufflator 703 that produces a stream of insufflation gasesat a pressure above atmospheric for delivery into the patient 705abdominal or peritoneal cavity. The gases pass into a humidifier 707,including a heater base 709 and humidifier chamber 711, with the chamber711 in use in contact with the heater base 709 so that the heater base709 provides heat to the chamber 711. In the humidifier 707, theinsufflation gases are passed through the chamber 711 so that theybecome humidified to an appropriate level of moisture.

The system 701 includes a delivery conduit 713 that connects between thehumidifier chamber 711 and the patient 705 peritoneal cavity or surgicalsite. The conduit 713 has a first end and second end, the first endbeing connected to the outlet of the humidifier chamber 711 andreceiving humidified gases from the chamber 711. The second end of theconduit 713 is placed in the patient 705 surgical site or peritonealcavity and humidified insufflation gases travel from the chamber 711,through the conduit 713 and into the surgical site to insufflate andexpand the surgical site or peritoneal cavity. The system also includesa controller (not shown) that regulates the amount of humidity suppliedto the gases by controlling the power supplied to the heater base 709.The controller can also be used to monitor water in the humidifierchamber 711. A smoke evacuation system 715 is shown leading out of thebody cavity of the patient 705.

The smoke evacuation system 715 can be used in conjunction with theinsufflation system 701 described above or may be used with othersuitable insufflation systems. The smoke evacuation system 715 comprisesa discharge or exhaust limb 717, a discharge assembly 719, and a filter721. The discharge limb 717 connects between the filter 721 and thedischarge assembly 719, which in use is located in or adjacent to thepatient 705 surgical site or peritoneal cavity. The discharge limb 717is a self-supporting tube (that is, the tube is capable of supportingits own weight without collapsing) with two open ends: an operative siteend and an outlet end.

At least one embodiment includes the realization that the use of acomposite tube as the conduit 713 can deliver humidified gases to thepatient 705 surgical site with minimized heat loss. This canadvantageously reduce overall energy consumption in the insufflationsystem, because less heat input is needed to compensate for heat loss.

Coaxial Tube

A coaxial breathing tube can also comprise a composite tube as describedabove. In a coaxial breathing tube, a first gas space is an inspiratorylimb or an expiratory limb, and the second gas space is the other of theinspiratory limb or expiratory limb. One gas passageway is providedbetween the inlet of said inspiratory limb and the outlet of saidinspiratory limb, and one gas passageway is provided between the inletof said expiratory limb and the outlet of said expiratory limb. In oneembodiment, the first gas space is said inspiratory limb, and the secondgas space is said expiratory limb. Alternatively, the first gas spacecan be the expiratory limb, and the second gas space can be theinspiratory limb.

Reference is next made to FIG. 7, which shows a coaxial tube 701according to at least one embodiment. In this example, the coaxial tube701 is provided between a patient 701 and a ventilator 705. Expiratorygases and inspiratory gases each flow in one of the inner tube 707 orthe space 709 between the inner tube 707 and the outer tube 711. It willbe appreciated that the outer tube 711 may not be exactly aligned withthe inner tube 707. Rather, “coaxial” refers to a tube situated insideanother tube.

For heat transfer reasons, the inner tube 707 can carry the inspiratorygases in the space 713 therewithin, while the expiratory gases arecarried in the space 709 between the inner tube 707 and the outer tube711. This airflow configuration is indicated by arrows. However, areverse configuration is also possible, in which the outer tube 711carries inspiratory gases and the inner tube 707 carries expiratorygases.

In at least one embodiment, the inner tube 707 is formed from acorrugated tube, such as a Fisher & Paykel model RT100 disposable tube.The outer tube 711 can be formed from a composite tube, as describedabove.

With a coaxial tube 701, the ventilator 705 may not become aware of aleak in the inner tube 707. Such a leak may short circuit the patient701, meaning that the patient 701 will not be supplied with sufficientoxygen. Such a short circuit may be detected by placement of a sensor atthe patient end of the coaxial tube 701. This sensor may be located inthe patient end connector 715. A short circuit closer to the ventilator705 will lead to continued patient 701 re-breathing of the air volumeclose to the patient 701. This will lead to a rise in the concentrationof carbon dioxide in the inspiratory flow space 713 close to the patient701, which can be detected directly by a CO₂ sensor. Such a sensor maycomprise any one of a number of such sensors as is currentlycommercially available. Alternatively, this re-breathing may be detectedby monitoring the temperature of the gases at the patient end connector715, wherein a rise in temperature above a predetermined level indicatesthat re-breathing is occurring.

In addition to the above to reduce or eliminate the formation ofcondensation within either the inner tube 707 or outer tube 711, and tomaintain a substantially uniform temperature in the gases flow throughthe coaxial tube 701, a heater, such as a resistance heater filament,may be provided within either the inner tube 707 or outer tube 711,disposed within the gases spaces 709 or 713, or within the inner tube707 or outer tube 711 walls themselves.

Thermal Properties

In embodiments of a composite tube 201 incorporating a heating filament215, heat can be lost through the walls of the first elongate member203, resulting in uneven heating. As explained above, one way tocompensate for these heat losses is to apply an external heating sourceat the first elongate member 203 walls, which helps to regulate thetemperature and counter the heat loss. Other methods for optimizingthermal properties can also be used, however.

Reference is next made to FIGS. 9A through 9C, which demonstrate exampleconfigurations for bubble height (that is, the cross-sectional height ofthe first elongate member 203 measured from the surface facing the innerlumen to the surface forming the maximum outer diameter) to improvethermal properties.

The dimensions of the bubble can be selected to reduce heat loss fromthe composite tube 201. Generally, increasing the height of the bubbleincreases the effective thermal resistance of the tube 201, because alarger bubble height permits the first elongate member 203 to hold moreinsulating air. However, it was discovered that, at a certain bubbleheight, changes in air density cause convection inside the tube 201,thereby increasing heat loss. Also, at a certain bubble height thesurface area becomes so large that the heat lost through surfaceoutweighs the benefits of the increased height of the bubble. Certainembodiments include these realizations.

The radius of curvature and the curvature of the bubble can be usefulfor determining a desirable bubble height. The curvature of an object isdefined as the inverse of the radius of curvature of that object.Therefore, the larger a radius of curvature an object has, the lesscurved the object is. For example, a flat surface would have a radius ofcurvature of ∞, and therefore a curvature of 0.

FIG. 9A shows a longitudinal cross-section of a top portion of acomposite tube. FIG. 9A shows an embodiment of a composite tube 201where the bubble has a large height. In this example, the bubble has arelatively small radius of curvature and therefore a large curvature.Also, the bubble is approximately three to four times greater in heightthan the height of the second elongate member 205.

FIG. 9B shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 9B shows an embodiment of a composite tube 201where the bubble is flattened on top. In this example, the bubble has avery large radius of curvature but a small curvature. Also, the bubbleis approximately the same height as the second elongate member 205.

FIG. 9C shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 9C shows an embodiment of a composite tube 201where the width of the bubble is greater than the height of the bubble.In this example, the bubble has radius of curvature and the curvaturebetween that of FIG. 9A and FIG. 9B, and the center of the radius forthe upper portion of the bubble is outside of the bubble (as compared toFIG. 9A). The inflection points on the left and right sides of thebubble are about at the middle (heightwise) of the bubble (as opposed toin the lower portion of the bubble, as in FIG. 9A). Also, the height ofthe bubble is approximately double that of the second elongate member205, resulting in a bubble height between that of FIG. 9A and FIG. 9B.

The configuration of FIG. 9A resulted in the lowest heat loss from thetube. The configuration of FIG. 9B resulted in the highest heat lossfrom the tube. The configuration of FIG. 9C had intermediate heat lossbetween the configurations of FIGS. 9A and 9B. However, the largeexternal surface area and convective heat transfer in the configurationof FIG. 9A led to inefficient heating. Thus, of the three bubblearrangements of FIGS. 9A-9C, FIG. 9C was determined to have the bestoverall thermal properties. When the same thermal energy was input tothe three tubes, the configuration of FIG. 9C allowed for the largesttemperature rise along the length of the tube. The bubble of FIG. 9C issufficiently large to increase the insulating air volume, but not largeenough to cause a significant convective heat loss. The configuration ofFIG. 9B was determined to have the poorest thermal properties, namelythat the configuration of FIG. 9B allowed for the smallest temperaturerise along the length of the tube. The configuration of FIG. 9A hadintermediate thermal properties and allowed for a lower temperature risethan the configuration of FIG. 9C.

It should be appreciated that although the FIG. 9C configuration may bepreferred in certain embodiments, other configurations, including thoseof FIGS. 9A, 9B and other variations, may be utilized in otherembodiments as may be desired.

TABLE 7 shows the height of the bubble, the outer diameter of the tube,and the radius of curvature of the configurations shown in each of FIGS.9A, 9B, and 9C.

TABLE 7 Tube (FIG.) 9A 9B 9C Bubble height (mm) 3.5 5.25 1.75 Outerdiameter (mm) 21.5 23.25 19.75 Radius of curvature (mm) 5.4 3.3 24.3

TABLE 7A shows the height of the bubble, the outer diameter and theradius of curvature of further configurations as shown in FIGS. 11A,11B, and 11C.

TABLE 7A Tube (FIG.) 11A 11B 11C Bubble height (mm) 6.6 8.4 9.3 Outerdiameter (mm) 24.6 26.4 27.3 Radius of curvature (mm) 10 8.7 5.7

It should be noted that, in general, the smaller the radius ofcurvature, the tighter the tube can be bent around itself without thebubble collapsing or “kinking.” For example, FIG. 11D shows a tube thathas been bent beyond its radius of curvature (specifically, it shows thetube of FIG. 11A bent around a radius of curvature of 5.7 mm), therebycausing kinking in the walls of the bubble. Kinking is generallyundesirable, as it can detract from the appearance of the tube, and canimpair the thermal properties of the tube.

Accordingly, in some applications, configurations with increased bendingproperties (such as those shown in FIG. 9A or 9B) can be desirabledespite having less efficient thermal properties. In some applications,it has been found that a tube with an outer diameter of 25 mm to 26 mm(or about 25 mm to about 25 mm) provides a good balance between thermalefficiency, flexibility, and bending performance. It should beappreciated that although the configurations of FIGS. 9A and 9B may bepreferred in certain embodiments, other configurations, including thoseof FIGS. 11A-11D and other variations, may be utilized in otherembodiments as may be desired.

Reference is next made to FIGS. 9C through 9F which demonstrate examplepositioning of heating element 215 with similar bubble shapes to improvethermal properties. The location of the heating element 215 can changethe thermal properties within the composite tube 201.

FIG. 9C shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 9C shows an embodiment of a composite tube 201where the heating elements 215 are centrally located in the secondelongate member 205. This example shows the heating elements 215 closeto one another and not close to the bubble wall.

FIG. 9D shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 9D shows an embodiment of a composite tube 201 inwhich the heating elements 215 are spaced farther apart, as compared toFIG. 9C, in the second elongate member 205. These heating elements arecloser to the bubble wall and provide for better regulation of heatwithin the composite tube 201.

FIG. 9E shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 9E shows an embodiment of a composite tube 201wherein the heating elements 215 are spaced on top of each other in thevertical axis of the second elongate member 205. In this example, theheating elements 215 are equally close to each bubble wall.

FIG. 9F shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 9F shows an embodiment of a composite tube 201where the heating elements 215 are spaced at opposite ends of the secondelongate member 205. The heating elements 215 are close to the bubblewall, especially as compared to FIGS. 9C-9E.

Of the four filament arrangements of FIGS. 9C-9F, FIG. 9F was determinedto have the best thermal properties. Because of their similar bubbleshapes, all of the configurations experienced similar heat loss from thetube. However, when the same thermal energy was input to the tubes, thefilament configuration of FIG. 9F allowed for the largest temperaturerise along the length of the tube. The configuration of FIG. 9D wasdetermined to have the next best thermal properties and allowed for thenext largest temperature rise along the length of tube. Theconfiguration of FIG. 9C performed next best. The configuration of FIG.9E had the poorest performance and allowed for the smallest temperaturerise along the length of the tube, when the same amount of heat wasinput.

It should be appreciated that although the FIG. 9F configuration may bepreferred in certain embodiments, other configurations, including thoseof FIGS. 9C, 9D, 9E, and other variations, may be utilized in otherembodiments as may be desired.

Reference is next made to FIGS. 10A through 10C, which demonstrateexample configurations for stacking of the first elongate member 203. Itwas discovered that heat distribution can be improved in certainembodiments by stacking multiple bubbles. These embodiments can be morebeneficial when using an internal heating filament 215. FIG. 10A shows alongitudinal cross-section of a top portion of another composite tube.FIG. 10A shows a cross section of a composite tube 201 without anystacking.

FIG. 10B shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 10B shows another example composite tube 201 withstacked bubbles. In this example, two bubbles are stacked on top of eachother to form the first elongate member 203. As compared to FIG. 10A,the total bubble height is maintained, but the bubble pitch is half ofFIG. 10A. Also, the embodiment in FIG. 10B has only a slight reductionin air volume. The stacking of the bubbles reduces natural convectionand heat transfer in the gap between bubbles 213 and lowers the overallthermal resistance. The heat flow path increases in the stacked bubblesallowing heat to more easily distribute through the composite tube 201.

FIG. 10C shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 10C shows another example of a composite tube 201with stacked bubbles. In this example, three bubbles are stacked on topof each other to form the first elongate member 203. As compared to FIG.10A, the total bubble height is maintained, but the bubble pitch is athird of FIG. 10A. Also, the embodiment in FIG. 10B has only a slightreduction in air volume. The stacking of the bubbles reduces naturalconvection and heat transfer in the gap between bubbles 213.

Cleaning

In at least one embodiment, materials for a composite tube can beselected to handle various methods of cleaning. In some embodiments,high level disinfection (around 20 cleaning cycles) can be used to cleanthe composite tube 201. During high level disinfection, the compositetube 201 is subject to pasteurization at about 75° C. for about 30minutes. Next, the composite tube 201 is bathed in 2% glutaraldehyde forabout 20 minutes. The composite tube 201 is removed from theglutaraldehyde and submerged in 6% hydrogen peroxide for about 30minutes. Finally, the composite tube 201 is removed from the hydrogenperoxide and bathed in 0.55% orthophthalaldehyde (OPA) for about 10minutes.

In other embodiments, sterilization (around 20 cycles) can be used toclean the composite tube 201. First, the composite tube 201 is placedwithin autoclave steam at about 121° C. for about 30 minutes. Next, thetemperature of the autoclave steam is increased to about 134° C. forabout 3 minutes. After autoclaving, the composite tube 201 is surroundedby 100% ethylene oxide (ETO) gas. Finally, the composite tube 201 isremoved from the ETO gas and submerged in about 2.5% glutaraldehyde forabout 10 hours.

The composite tube 201 may be made of materials to withstand therepeated cleaning process. In some embodiments, part or all of thecomposite tube 201 can be made of, but is not limited to,styrene-ethylene-butene-styrene block thermo plastic elastomers, forexample Kraiburg TF6STE. In other embodiments, the composite tube 201can be made of, but is not limited to, hytrel, urethanes, or silicones.

The foregoing description of the invention includes preferred formsthereof. Modifications may be made thereto without departing from thescope of the invention. To those skilled in the art to which theinvention relates, many changes in construction and widely differingembodiments and applications of the invention will suggest themselveswithout departing from the scope of the invention as defined in theappended claims. The disclosures and the descriptions herein are purelyillustrative and are not intended to be in any sense limiting.

What is claimed is:
 1. A composite tube for use in medical circuits forproviding gases to and/or removing gases from a patient, the compositetube comprising: a first elongate member comprising a cross-sectionalshape that defines a hollow body spirally wound to form at least in partan elongate tube having a longitudinal axis, a lumen extending along thelongitudinal axis, and a hollow wall defining a hollow space and atleast partially surrounding the lumen; and a second elongate memberspirally wound and joined at bond regions to the first elongate memberbetween adjacent turns of the first elongate member, wherein surfaceportions of each of the first elongate member and the second elongatemember form at least a portion of the lumen of the elongate tube, thefirst elongate member having a first surface that extends external tothe lumen between adjacent bond regions and a second surface that formsa portion of the lumen between the adjacent bond regions, the firstsurface having a greater length than the second surface when the firstelongate member is viewed normal to the cross sectional shape of thefirst elongate member, wherein one or more conductive filaments areembedded or encapsulated in the second elongate member.
 2. The compositetube of claim 1, wherein the second elongate member is less flexiblethan the first elongate member.
 3. The composite tube of claim 1,wherein the spirally wound and joined first and second elongate membersprovide crush resistance while being flexible enough to permitshort-radius bends without kinking, occluding or collapsing.
 4. Thecomposite tube of claim 1, wherein portions of the first elongate memberoverlap adjacent turns of the second elongate member.
 5. The compositetube of claim 1, wherein the second elongate member is solid orsubstantially solid.
 6. The composite tube of claim 1, wherein the firstelongate member forms in longitudinal cross-section a plurality ofbubbles with the second surface defining a flattened surface at thelumen.
 7. The composite tube of claim 6, wherein the bubbles haveperforations.
 8. The composite tube of claim 1, wherein the secondelongate member has a longitudinal cross-section that is generallytriangular, generally T-shaped, or generally Y-shaped, and wherein atleast two of the one or more conductive filaments are embedded orencapsulated on opposite sides of the triangle, T-shape, or Y-shape. 9.The composite tube of claim 1, wherein the one or more conductivefilaments is a heating filament.
 10. The composite tube of claim 1,wherein the one or more conductive filaments is a sensing filament. 11.The composite tube of claim 1, comprising a plurality of conductivefilaments embedded or encapsulated in the second elongate member. 12.The composite tube of claim 1, comprising four conductive filamentsembedded or encapsulated in the second elongate member.
 13. Thecomposite tube of claim 1, wherein pairs of conductive filaments areformed into a connecting loop at one end of the composite tube.
 14. Thecomposite tube of claim 1, wherein the one or more filaments are spacedfrom the lumen wall.
 15. The composite tube of claim 1 being a medicalcircuit component, an inspiratory tube, an expiratory tube, a PAPcomponent, an insufflation component, an exploratory component, or asurgical component.
 16. A method of manufacturing a composite tube foruse in medical circuits for providing gases to and/or removing gasesfrom a patient, the method comprising: providing a first elongate membercomprising a cross-sectional shape that forms a hollow body defining ahollow space and a second elongate member, the second elongate membercomprising one or more conductive filaments; spirally wrapping thesecond elongate member around a mandrel with opposite side edge portionsof the second elongate member being spaced apart on adjacent wraps,thereby forming a second-elongate-member spiral; and spirally wrappingthe first elongate member that defines the hollow space around thesecond-elongate-member spiral to form a lumen, such that portions of thefirst elongate member overlap adjacent wraps of thesecond-elongate-member spiral at bond regions and a portion of the firstelongate member is disposed adjacent the mandrel in the space betweenthe wraps of the second-elongate-member spiral, the first elongatemember having a first surface that extends external to the lumen betweenadjacent bond regions and a second surface that forms a portion of thelumen between the adjacent bond regions, the first surface having agreater length than the second surface when the first elongate member isviewed normal to the cross sectional shape of the first elongate member,thereby forming a first-elongate-member spiral such that surfaceportions of each of the first elongate member and the second elongatemember are located adjacent the mandrel.
 17. The method of claim 16,further comprising supplying air at a pressure greater than atmosphericpressure to an end of the first elongate member.
 18. The method of claim16, further comprising cooling the second-elongate-member spiral and thefirst-elongate-member spiral to form the composite tube having the lumenextending along a longitudinal axis and the hollow space surrounding thelumen.
 19. The method of claim 16, further comprising forming the firstand/or second elongate member.
 20. The method of claim 19, whereinforming the first and/or second elongate member comprises extruding thefirst and/or second elongate member with a first and/or second extruder,respectively, the first extruder distinct from the second extruder. 21.The method of claim 19, where forming the second elongate membercomprises embedding the one or more conductive filaments in the secondelongate member.
 22. The method of claim 16, wherein the conductivefilaments are non-reactive with the second elongate member.
 23. Themethod of claim 16, wherein the one or more conductive filamentscomprise aluminum or copper.
 24. The method of claim 16, furthercomprising forming pairs of the one or more conductive filaments into aconnecting loop at one end of the composite tube.